Sunday, 21 October 2012

Does QM really imply non-causality?

Does quantum physics really contend that particles can actually appear and disappear (and then reappear) into our time and space dimension without any outside cause or is it only a matter of that their measurement of them makes it appear like they do that?

Response: The correct interpretation of Quantum Mechanics is still hotly debated. It seems as if many possible interpretations (Copenhagen, Bohm, Many-worlds) are compatible with the equations and all the physical evidence. And no-one knows how to reconcile Quantum Mechanics and General Relativity, let alone how/whether String/M theory is correct.

So certainly in Hawking's highly speculative cosmology and interpretation things can happen "without any outside cause" and we do know that particles spontaneously appear and disappear in the so-called Quantum Vacuum - at a micro level this is very well confirmed by observation.

However (as John keeps pointing out) it is a ridiculous abuse of language to call the Quantum Vacuum "nothing" - this so called "empty space" is teeming with energy and an almost infinite number of particles.  Even if the existence of the Universe is a consequence of the laws of physics (and you can always formulate a set of laws of physics that "require" the universe to exist) this does not, and can not, address the question of WHY the laws of physics have the form that they do.  Hawking would suggest that anthropic selection answers this but that's really begging the question.

Further Question: Does changing the very beginning of time and space from a single point to a less than distinct point really change the Big Bang’s occurrence from an external causality to itself?

Response: No it's a mathematical "trick" with no real philosophical implications, though of course it might look as though it had. As St Augustine realised in the 5th century, the "need" for God does not depend on whether there is a first moment in time - but why is there time at all? You can always mathematically re-scale "time" so that it has no beginning and re-write the laws of physics appropriately.

As noted above, no-one knows how QM and GR reconcile. QM doesn't like singularities. Until there is much clearer empirical evidence the scope for clever speculation is endless, and Hawking is very clever and certainly offers deep insights (which may or may not be correct) at a physical level.  But he is no theologian/philosopher and doesn't seem to understand that his theories have nothing to do with the existence of God at all.

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